Hey guys, i have a tough one for you. I have an 87 Iroc. I want to use my 89 corvette chip in it. It doesnt start with the vette chip. Looking at schematics for the VATS module and ECM, I see that the module senses the resistor in the key, and grounding a certain pin to the ECM (looks like the Cranking fuel enable input). NE1 ever done this before? I also wanna eliminate the cold start valve to. I cannot find the VATS module in my 89 Formula, but i know it has it. Can anyone help me?

 

I was thinking on grounding that pin.

 

the VATS module doesn't ground that pin. It sends some kind of square wave signal to the ecm.

you will have to wire in the VATS module, or get a custom chip that has VATS disabled

 

the schematic shows it switching to ground. The cranking fuel enable input is just switched to ground. I cant see anything that would generate a signal

 

its a +5 volt dc reference voltage that just gets grounded from the ecm.

 

dude, ur right about the 50 hertz square wave, but that is different than the blue wire thats grounded.

 

dude, i have an idea, with the chip with vats is in my 87 Iroc, i think theres spark but no fuel. im wondering if i energize my fuel pump relay when the ingnition key is turned, if it would work?
gosh dern VATS!!!!

 

ah, i see it now, it is a 50 herts signal. 0 to 5 volts on and off. looks like a 50% duty cycle. yOU KNOW I CAN BUILD this circuit to duplicate this output.

 

That won't work either. The ecm cuts off fuel by not pulsing the injectors, not by disabling the fuel pump.

If you have access to the car the chip came from, try to get it's VATS module. It's way far up underneath the passenger side of the dashboard somewhere.

If you can build a device to fake that signal, that will work too.

 

Wouldn't it be easier to just get the corect chip?

 

this is the correct chip. the 85-88 tpi cars had a cold start valve. the 89's were the only mass air car with out it. but there is that vats problem, but i have figured out how to bypass the vats. im going to build a 50 hertz generator out of a 555 timer, and connect it to pin B6 of the computer. that is all that the vats did anyway. all the vats is is a frequency generator, and the chip in the key is a certain resistance to make a frequency. the right frequency sends 50 hertz +5 volts square wave to the cranking fuel enable pin. You have to give credit to the VATS Demi Gods at GM, but i am better

 

I do have the schematic if ne1 needs it.

 

I have an 87 TPI car with the cold start injector removed. I'm having someone burn a custom 89 bin with vats disabeled on my chip. But if you could build that thing then go for it.

 

You don't need to add hardware, the VAT's can be disabled in the EPROM.

A quick trip to the DIY-PROM board will get you squared away.

 

how do i find thid board?the DIY-PROM board ?

 

actually, if i built this circuit, i could run all the chips i bought for the tpi. i have like 3 vette chips and some Iroc chips. the vette chips seem more agressive and seem to pull better beyond 4000 rpms I did notice i didnt have to advance the timming with the vette chips, mostly the 89.

 

It's on the Tech Board page...here's the link:

https://www.thirdgen.org/techbb2/for...?s=&forumid=16

 

Thanks Mike